Raw paper is usually used as a substrate of photographic printing paper. In order to impart water resistance to the raw paper, a polyolefin resin, such as polyethylene, is coated on both surfaces of the raw paper. In a support for photographic printing paper, using raw paper coated with such a polyolefin resin, the surface on which a photographic emulsion layer is coated is called a "top surface", and the surface on which no photographic emulsion layer is coated is called a "back surface".
It is desirable that the back surface can be written on with a ball point pen, a fountain pen, or a pencil, for example.
For the purpose of automatically cutting by clearly indicating the boundary between a picture cut and a picture cut of a silver halide photographic material in a roll-form, or for the purpose of writing information concerning a picture cut, type writing is sometimes applied onto a back coat layer on the back surface of the silver halide photographic material in a printer.
A problem arises in that when the ink flows in a processing bath and the color becomes faded, the photographic printing paper does not sufficiently perform properly. Thus, a support for photographic printing paper which is freed from the above problem is desired.
However, since the polyolefin resin layer covering the surface of the raw paper usually does not have ink absorbility, when an ink is applied thereon, drying of the ink is slow, and moreover the ink after drying readily disappears by friction (by rubbing with a hand, for example) and is easily scratched in writing. Moreover, when a printing paper is superposed, the information written or typed is easily transferred to the surface of another printing paper. Thus there is a disadvantage that it is difficult to write characters or figures with a pencil or fountain pen on the surface of the polyolefin resin layer.
Although the above defect is improved by roughening the surface of the polyolefin resin layer by sand blast or embossing, or by a method of etching the surface with an acid, for example, it cannot be said that writing properties are sufficiently satisfactory.
Thus, heretofore, in order to overcome the above problems, for example, a method of incorporating an inorganic pigment of 1 to 40 .mu.m into the polyolefin resin layer on the back surface (JP-A-55-43528 (the term "JP-A" as used herein means an "unexamined published Japanese patent application)), a method of providing a layer comprising a water-soluble polymer, such as polyvinyl alcohol or carboxymethyl cellulose, and water-soluble silica sol (JP-B-44-14884 (the term "JP-B" as used herein means an "examined published Japanese patent application"), corresponding to U.S. Pat. No. 3,520,242), a method of providing a layer comprising a water-insoluble polymer emulsion, such as a polyethylene emulsion, and water-soluble silica sol (JP-B-50-36565, corresponding to U.S. Pat. No. 3,676,189), and a method of providing a coated layer containing a pigment, such as clay, and having moisture absorbing properties (JP-A-52-169426) have been proposed.
These methods, however, have the following problems. For example, when an inorganic pigment of 1 to 40 .mu.m is incorporated into the polyolefin resin layer on the back surface, a problem arises in that the resin layer is cracked, or contamination with the pigment occurs. Moreover, in the coated layer of the conventionally used composition, to obtain sufficiently satisfactory writing properties with a pencil, the coating amount should be controlled to about 5 g/m.sup.2 and in some cases, to more than 10 g/m.sup.2. Thus, there are many limitations in the process of production, such as a drying step of the coated layer.
In the photographic developing step, the coated layer is removed or dissolved, or after development, the pigment is removed only by slight friction. Thus, problems occur concerning the quality, such as contamination of the photographic printing paper.
Moreover, for the purpose of decreasing the cost of the product, the treatment solution is continuously recycled in the developing treatment system of the silver halide photographic material. In this case, the oxidized product of an organic compound dissolved from the photographic material into the treatment solution tends to accumulate therein as a contamination substance, which disadvantageously adheres to the support, in particular, on the back surface thereof.
The above disadvantages results in the unsatisfactory writing properties of the polyolefin resin layer on the back surface of the photographic printing paper. Also, written information is transferred to the top surface of another printing paper, contamination is caused by a contaminating substance and the coated layer provided to overcome the above disadvantages is subject to elution or removal during the developing processing. These problems have been addressed by providing a print-storing layer in which an inorganic pigment having a number average particle diameter of 0.1 to 3.0 .mu.m and an oil absorption amount of not more than 100 ml/100 g is dispersed in a binder including a styrene-acrylate copolymer, on the back surface of the support (see JP-A-62-6256). However, further improvements in ink printing properties, controlling contamination during the developing processing, and so forth are desired.
As a result of investigations to overcome the above problems, it has been found in the present invention that ink printing properties and contamination are markedly improved by using colloidal silica as an inorganic pigment and, at the same time, by using an aqueous dispersion of styrene-acrylate obtained by polymerizing in the presence of a water-soluble polymer.